Process for the synthesis of metal oxides of high specific surface area and high porosity, oxides obtained and catalysts containing the said oxides

Abstract

A process is provided for the synthesis for metal oxides of high specific surface area and high porosity which are particularly useful as catalyst supports. The process comprises forming a mixture of a salt of at least one metal and a molten salt medium comprising at least one alkali metal salt having an oxidizing effect, maintaining this mixture at the reaction temperature for the time necessary to convert the salt to oxide and thereafter isolating the metal oxide formed.

We claim: 
     
       1. Process for the synthesis of metal oxide of high specific surface area and high porosity which comprises forming a mixture of a salt of at least one metal and a molten salt medium comprising at least one alkali metal salt having an oxidizing effect and selected from the group consisting of alkali metal nitrates and sulfates, maintaining said mixture at a reaction temperature and time to convert the salt of at least one metal to a metal oxide, and isolating the metal oxide formed. 
     
     
       2. Process according to claim 1, wherein the alkali metal salt having an oxidizing effect is an alkali metal nitrate. 
     
     
       3. Process according to claim 1, wherein the molten salt medium comprises a eutectic mixture of two alkali metal salts. 
     
     
       4. Process according to claim 3, wherein the eutectic mixture is a mixture of sodium nitrate and potassium nitrate. 
     
     
       5. Process according to claim 1, wherein the reaction temperature varies between 250° and 550° C. 
     
     
       6. Process according to claim 1, wherein the reaction time is between 30 minutes and 2 hours. 
     
     
       7. Process according to claim 1, wherein the alkali metal salt having an oxidizing effect is used in large stoichiometric excess with respect to the metal salt. 
     
     
       8. Process according to claim 1, wherein the metal oxide formed is isolated by filtering off following removal of the oxidizing alkali metal salts by washing with water. 
     
     
       9. Process according to claim 1, wherein the metal oxide is an oxide of at least one metal of groups 3 and 4 of the periodic classification of the elements. 
     
     
       10. Process according to claim 9, wherein the metal oxide is at least one refractory oxide, from the group consisting of zirconium oxide, aluminium oxide, silicon oxide and titanium oxide. 
     
     
       11. Process according to claim 10, wherein the metal oxide is zirconium oxide or a zirconium oxide/alumina mixture. 
     
     
       12. At least one metal oxide of high specific surface area and high porosity selected from the group consisting of zirconium oxide, alumina, silica, titanium oxide, and mixtures thereof, obtained by a process which comprises forming a mixture of a salt of at least one metal and a molten salt medium comprising at least one alkali metal salt having an oxidizing effect and selected from the group consisting of alkali metal nitrates and sulfates, maintaining said mixture at a reaction temperature and time to convert the salt of at least one metal to a metal oxide, and isolating the metal oxide formed. 
     
     
       13. Process according to claim 1, wherein the alkali metal salt having an oxidizing effect is used in a stoichiometric excess of 2 to 3 with respect to the metal salt. 
     
     
       14. A catalyst for the conversion of organic compounds comprising support which contains at least one metal oxide according to claim 12. 
     
     
       15. A catalyst according to claim 14 wherein said at least one metal oxide is zirconium oxide or zirconium oxide/alumina. 
     
     
       16. A catalyst according to claim 14 further comprising an active phase containing a nickel molybdenum.